Answer:
0 is the answer assuming the whole thing is a fraction where the numerator is f(a+h)-f(a) and the denominator is h.
Explanation:
If the expression for f is really a constant, then the difference quotient will lead to an answer of 0.
If the extra for f is linear (including constant expressions), the difference quotient will be the slope of the expression.
However, let's go about it long way for fun.
If f(x)=5, then f(a)=5.
If f(x)=5, then f(a+h)=5.
If f(a)=5 and f(a+h)=5, then f(a+h)-f(a)=0.
If f(a+h)-f(a)=0, then [f(a+h)-f(a)]/h=0/h=0.